1. Field of the Invention
The present invention relates to a controller for controlling a heater which heats the interior of an automotive passenger compartment or the like.
2. Description of the Related Art
Conventional automotive passenger compartments are heated by introducing a coolant from the internal combustion engine via a coolant pipe into a heater assembly composed of a heater core and a blower, and passing air through the heater assembly so that the air heated by the heater core through heat exchange can be used for heating purpose.
The above arrangement utilizing an engine coolant is however disadvantageous for the following reasons: Since it takes more than 10 minutes for a gasoline engine or more than 20 minutes for a diesel engine to be warmed up, the coolant is not available for heating the compartment during that time interval. Therefore, especially in colder climates, passengers are required to wear clothes designed for cold weather protection in the compartment during such a warm-up interval. Further, the defroster for removing frost or ice from the window glass sheets does not work well until the temperature of the coolant is high enough.
Another problem with the conventional heaters is that when the automobile is running down a long downward slope, the coolant temperature may fall to the extent that the coolant is no longer effective in heating the compartment. Since a diesel engine, in particular, is of the type in which an air-fuel mixture is compressed in each engine cylinder and ignited by the heat produced by the compression of the air-fuel mixture under high pressure, the temperature of the exhaust gas and the coolant temperature are highly apt to decrease upon travel down a downward slope because only a light load is imposed on the engine on the downward slope. Furthermore, the diesel engine tends to produce white smoke and odor due to incomplete fuel combustion under cold conditions.
To eliminate the above drawbacks, the applicant has filed Japanese Patent Application No. 59-106869 for an automotive heater in which a burner is provided in the air intake pipe of an engine and a heat exchanger is disposed downstream of the burner, so that heat produced by burning fuel in the burner will be recovered by the heat exchanger as a heat source.
A control device for controlling the temperatures of an atomizing glow plug in a fuel atomizer of the burner and an igniting glow plug for igniting atomized fuel has respective bridges for the glow plugs, making a control mechanism somewhat complex.